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Update README for z.record key type schema #1168

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May 25, 2022
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Update README for z.record key type schema #1168

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Update README for z.record key type schema
gtarsia May 25, 2022
1b71f5c
Replace nonempty() usage with min(1)
gtarsia May 25, 2022
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17 changes: 15 additions & 2 deletions README.md
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Expand Up @@ -1046,7 +1046,7 @@ const item = z

Record schemas are used to validate types such as `{ [k: string]: number }`.

If you want to validate the _values_ of an object against some schema but don't care about the keys, use `Record`.
If you want to validate the _values_ of an object against some schema but don't care about the keys, use `z.record(valueType)`:

```ts
const NumberCache = z.record(z.number());
Expand All @@ -1069,9 +1069,22 @@ userStore["77d2586b-9e8e-4ecf-8b21-ea7e0530eadd"] = {
}; // TypeError
```

### Record key type

If you want to validate both the keys and the values, use
`z.record(keyType, valueType)`:

```ts
const NoEmptyKeysSchema = z.record(z.string().min(1), z.number());
NoEmptyKeysSchema.parse({ 'count': 1 }) // => { 'count': 1 }
NoEmptyKeysSchema.parse({ '': 1 }) // fails
```

_(Notice how when passing two arguments, `valueType` is the second argument)_

**A note on numerical keys**

You may have expected `z.record()` to accept two arguments, one for the keys and one for the values. After all, TypeScript's built-in Record type does: `Record<KeyType, ValueType>` . Otherwise, how do you represent the TypeScript type `Record<number, any>` in Zod?
While `z.record(keyType, valueType)` is able to accept numerical key types and TypeScript's built-in Record type is `Record<KeyType, ValueType>`, it's hard to represent the TypeScript type `Record<number, any>` in Zod.

As it turns out, TypeScript's behavior surrounding `[k: number]` is a little unintuitive:

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